Knurling device



Oct. 6, 1953 c. F. JONES KNURLING DEVICE 2 Sheets-Sheet 1 Filed June 22, 1949 INVENTOR. I Ce r gwlzfones, BY

C. F. JONES KNURLING DEVICE Oct. 6, 1953 Filed June 22, 1949 2 Sheets-Sheet 2 BY 772911] Owe $4,00 I film/7 W Patented Oct. 6, 1953 KNURLING DEVICE Cernyw F. Jones, Economy, Ind., assignor to Perfect Circle Corporation, Hagerstown, Ind., a corporation of Indiana Application J une 22, 1949, Serial No. 100,649

1 Claim. 1

This invention relates generally to a knurling device for knurling the peripheral surface of a cylindrical object and more particularly to a device for knurling predetermined areas on the peripheral surface of a hollow cylindrical article such as a piston for an internal combustion engine.

With continued operation of an internal combustion engine, the pistons and cylinders tend to wear or become distorted with the result that the normal fit of the pistons within the cylinders is lost. This condition is often characterized by piston slap and other evidence of excessive looseness. The lack of a proper fit between the piston and the cylinder is objectionable since it impairs engine efficiency and has an adverse effect on the economy of operation.

Various means for correcting this condition have been employed, one method involving the expansion of the outer wall or skirt portion of the piston sufficiently to reestablish the normal fit between piston and cylinder. Such expansion may be accomplished, for example, by knurling the outer surface of the piston to form roughened areas on the thrust faces thereof having an interrupted surface comprising projecting portions with intervening depressions. During knurling the metal is extruded or swaged to a sufiicient extent so that the projections formed on the piston surface extend outwardly to the desired increased size whereby the proper fit between the piston and the cylinder is realized.

A machine or tool for knurling the outer surface of a hollow piston should preferably be provided with an anvil member or other supporting means adapted to engage and support the piston internally while a knurling element engages the exterior of the piston under pressure. However, the interior surface of the skirt portion of a piston is usually quite uneven in the area between the wrist pin bosses, because of various protuberances and surface irregularities such as reinforcing ribs, partial machining of the interior surface, and general surface roughness characteristic of cast articles. Thus, a satisfactory knurling device must be provided with means for accommodating the variations in piston wall thickness while at the same time permitting a substantially constant knurling pressure to be maintained against the outer surface of the piston.

Accordingly, one object of my invention is to provide a device for knurling the exterior surfaces of pistons which readily accommodates variations in piston wall thickness while permitting the application of a substantially constant knurling pressure.

Another object of my invention is to provide a device for knurling the exterior surfaces of pistons having a rigid supporting member for engaging the interior of the piston and a movable knurling member for engaging the exterior of the piston, the spacing between said members being variable under manual control by the operator whereby to accommodate protuberances and other irregularities on the interior surface of the piston.

An additional object of the invention is to provide a hand operated device for knurling the exterior surfaces of pistons which is of simple rugged construction and is relatively portable in the sense that it requires no permanent mounting and may, for example, be held in a vise or other bench type support.

A further object of my invention is to provide a simple hand-operated mechanism for knurling the exterior surfaces of pistons in combination with a steady rest to facilitate location of the piston prior to knurling.

Other objects and advantages of the invention will become apparent from the subsequent detailed description of the invention and the accompanying drawings in which:

Fig. 1 is a plan view of a knurling device comprising one specific embodiment of my invention;

Fig. 2 is an end view of the device as viewed from the right in Fig. 1;

Fig. 3 is a front elevational view of the device;

Fig. 4 is an end view of the device with portions thereof in section as taken along the line 4-4 of Fig.3; and

Fig. 5 is a sectional view taken along the line 5-5 of Fig. 4.

The knurling device comprising the present invention is provided with a pair of cooperating anvil and knurling elements, the anvil element being arranged to support the piston internally while the knurling elements bear against the outer surface of the piston. The knurling element is preferably in the form of a small roller which is applied to the outer surface of the piston in rolling relation therewith so that, by rolling the knurling roller on the surface, the resultant area knurled in one application of the tool comprises a band having a width equal to the width of the roller. Usually the roller is relatively narrow and traverses the piston circumferentially so that a plurality of such knurled bands are required to cover a desired area longitudinally of the piston. The knurled bands may, of course, be disposed in continuous abutting relation to one another or they may be slightly spaced from each other longitudinally of the piston.

With a piston for an internal combustion engine, it is necessary to knurl only the thrust faces of the piston skirt, i. e. those portions which are subjected to lateral thrust against the cylinder wall due to the position of the connecting rod Thus, the knurling operation may be restricted to the portions of the piston skirt lying intermediate the wristepin holes oirfoppositefsfides, the piston. The knurled area preferably starts immediately below the ring grooves at the upper end of the piston and may extend axially or Ion-- gitudinally for the full length of the piston skirt If desired, the knurled band at the extreme outer end of the skirt may be spaced; differently from the remaining bands in orderto position the outermost band as close as possible to the edge of the piston.

In addition to effecting expansion of the piston metal by extrusion thereof, in the manner hereinbefore described, whereby to reestablish a PIQDBR fi etweenthepiston and the cylinder, the knurled; surface. obtained by. my: invention 39 i G S. o her important-advantages. .Fon ex.-.. ample, ithasbeenfoundthat better-performance s.ob ai edinarecinme tme iston andx i n 1 1511 likeconstruction, ifzoneofithe twosure ces.- is of allinterrupted;naturecomprisingpro: jecting portions. withwintervening depressions, such as may be providedby knurling. resurface of this character has been found to run cooleran. an absolutely smooth. surface. for. pistons as well. as other. cylindrical objects. adapted tov reciprocate. within, a, bore. Another advantage. inherent in .knurling the. surfaces .of pistons and. ke. articles is, found in, the improved wearing. qualities of the. knurledsurface. resulting. from the hardening efieots of cold working. themetaL In addition, the interrupted surface. afforded by knurlingprovides aseries of pockets or"v reservoirs whichserve to retain, lubricatingoil: andthereby maintain a, continuous. supplyrof: lubricant at the surface-contacting areas.

Itwill be. apparent, therefore, that, in addition to the. obvious, utility ofknurling old-or. worn. pistonsin ordento. expand. the same, knurling. may also be resorteri to.in the,case .ofgnew..pis-.. tonsor. original; ,assemblieslof apistonswithin their cylinders. in .orden to, attain the other adYantages.-.

mentioned above. While the knurling devices 4 rigidly mounted anvil member and a cooperating knurling member mounted for pivotal movement toward and away from the anvil member in combination with manually operable lever means for controlling the knurling pressure.

Referring now to the drawings, which show by way of illustration one silei ififiemhodiment of my inventiqmthe deyice comprises an elongated body member or base, indicated generally at H, hav ing a central portion I2 adapted to be received between the clamping jaws of a vise or other clamping means for supporting the device. Projecting upwardly at one end of the base H is a pairof, longitudinally spaced upright brackets ii-9; extending rearwardly at their upper portions and overhanging the base H, as seen inostclearlyinllig e. A knurl support 14 in the general form of a lever or bell crank having a forwardlyextending socket portion l and a decomprising the present invention, are. designed.

mation. involving alternate. depressed; andraisedl;

portions, regardless: of; whether one on the; other or both, of. said. portions; are. continuousthrouglh. out theareahavinee suchformation. Thus. the

term includes; not, only. the .crissecross pattern. but also a pattern formed. by; parallel: grooves; or by isolated: indentations resulting-.- in connectedz.

raisedportions.

As hereinbeforementioned, an important ob jectof my invention is to providea knurling device'for pistons which is designed; to acc'ommoy date varying piston walli thicknesses due to in; 'terfial r d be ensss r surface. gulari s. e. at h s line. me .ii rmi tius. e 911 19 iubst ntia ly onstant nul i erres pending portion I6 is pivotally mounted on a pin on shaft [1. between thebr-ackets I3 for'rock-ing on pivotal movement. A knurlingmember inthe form of a roller l 8.is.journaledfor rolling move-. ment in the. depending -portion [.6 of the knurl' support I 4 and projects rearwardly'therefromtoa sl'ight extent, as indicated at I9 (Figs. 1 and 4). An elongated hand lever 20 having an operatingknobi Lfits into thesocket-portion [50f the knurl support It and isdetachably secured therein by means of a. screw 22:- adapted to engage aflattened: portion 23 on the lever 20.

The-knurlingroller I8 isrotatably-mounted in the knurl support [A by means ofa pair of bear-. ingsleeves 24 (Fig. 5 keyed tother'ollen t8; the bearing sleeves 24:. and the knurling roller- |8 be-- ing-clampedtogether'and securedtotheend:of an elongated drive shaft 25;by means of a stud-245 extending longitudinally through the sleeves and theroller-and threaded into the end:of theshaft- 25. A nut 21': issecured at the outer end-of the studzli for retaining the sleeves 24 and: the when l& inrclamped relation. The drive-shaft 25 ex tends longitudinally of=-t11e base H.- and is journaledatits oppositeend in. a depending link 28 pivotally'attached by means of a pin 29 toan overhanging bracket 3t, similar to-the brackets (3:, at theopposite end: of the-base; The=pin- 29 is aligned coaxially-with the pin- LT, and the distance betweenthe axis of: the pin ZBgand the .axis of-the. shaft. 25. is the. same asthe distance between. the axis ofthe pin I i-and the axis-of the shaft 25, whereby to permit swingingmmement ofzitheshaft 2izparalleling-the pivotal move-- ment of the knurl' support l4; A hand crank 32 extendsithrough an aperture adjacent-the;outer- 7 base i I rearwardly of'the bracket isan-anvilg ort ng, racket ha in n lpnsa edanri uplli r nserni i irieisi y eq re tthereto, s it a. ir. r c ew 31 nd tend n arallel; was. e. H dfihe r vesheit 1. e uterncst.

" Q. crime. ans. 61. 5; provi ed. with a pair, of...

spa edj rci g icnsbetwe n which s ioun 'esifor; emllius ncrement an anvil member he. m. shard inccthsu ec dr l er. 3a. hay ne.

approximately the same diameter andv width as,

the knurling roller, l8.

'r prqr sls astea y. r st-i itate- 0mins.

or lipsitiq ins a. pistes. L ha e iQe-Q mr o.r

ur ins a relsnsate aehav naanl utwame H best see m tinflli rtends ardiy rom... I accomplish this i i hrqedlr XPPQYlQlQB 8 ,75 the base ll at'the knurling end therepf g pistg 5. support, indicated generally at 42, is adjustably mounted on the bent end 4| of the arm 39 and is provided with a cradle or curved plate 43 at its upper portion for engaging the outer periphery of a piston, as shown in broken lines at 44. The lower portion of the piston support 42 below the bent end 4% of the arm 39 is split, as shown at 45, and is provided with a screw 46 threaded through the split portions thereof for clamping the support 42 to the bent end portion 4|. The opposite end of the arm 39 is provided with a flattened portion 4'! and is received within a connecting member 48 mounted on a supporting bar 49 which projects endwise from the base II. A clamping screw 5! extends through the connecting member 48 and engages the bar 49 for clamping the latter against the flattened surface 47 of the arm 39 whereby to secure the arm 39 at any desired angular position relative to the bar 49 and the base i i.

It will be seen that by rocking movement of the knurl support 14 about the pin I1, as effected by the hand lever 28, the knurling roller I8 may be moved away from and toward the anvil roller 38. During a knurling operation, the skirt portion of the piston 44 is clamped between the two rollers, the anvil roller 38 being disposed against the interior surface of the piston skirt and the knurling roller 13 hearing against the outer periphery of the piston skirt with the axes of the rollers being parallel to the axis of the piston. As the knurling roller I8 is swung rearwardly of the device toward the anvil roller 38 by downward pressure on the lever 20, the drive shaft 23 also swings rearwardly as the link 28 swings freely about the pin 29 through a path paralleling the movement of the depending portion [6 of the knurl support M.

In knurling a piston with the device shown in the drawings, the steady rest comprising the piston support 42 is adjusted as required to accommodate the size of the piston 44 to be knurled and to regulate the elevation of the piston above the base H so that the axis of the piston is in substantially the same horizontal plane as the axis of the anvil roller 38. When the piston 44 is thus properly positioned with its skirt portion in contact at its interior surface with the anvil roller 38, the steady res-t is clamped in position by means of the screws 46 and 5!.

With the lever 20 in lifted or raised position so that the knurling roller I8 is swung clear of the anvil roller 38, the skirt portion of the piston 44 is inserted between the rollers I8 and 38 to the desired extent. The knurling roller I8 is then moved into contact with the outer periphery of the piston skirt by downward movement of the hand lever 23 with sufficient hand pressure to sink the ridges of the knurling roller [8 into the skirt of the piston. In this position the piston 44 is stabilized by the clamping action of the rollers 38 and I8 and the knurling operation may then be carried out by rotating the hand crank 32 while the desired knurling pressure is controlled by the extent to which the operator presses down on the lever 20. Rotation of the hand crank 32 results in relative rolling movement between the knurling roller l8 and the piston 44 circumferentially of the latter. Because the skirt portion of the piston is clamped between the rollers l8 and 38, rotation of the knurling roller I8 also causes simultaneous rotation of the piston about its axis whereby to form an arcuate knurled band on the outer periphery of the skirt.

Because of the pivotal suspension of the knurling roller 18 between the supporting brackets [3, the operator of the knurling device can regulate the pressure with which the knurling roller I8 is pressed against the piston skirt while at the same time permitting the knurl support l4 to rock about the shaft IT and thereby swing the roller l3 forwardly of the device in order to accommodate variations in piston diameter as the latter rotates about its axis. If, during the course of a knurling operation, the anvil roller 33 encounters an internal protuberance or other surface irregularity on the interior of the piston skirt, it will be seen that because the anvil roller 33 is mounted in rigid relationship to the base: II, the piston 44 will be displaced in a horizontal plane forwardly of the device, 1. e. toward the.- As the piston 44 thus shifts. slightly in a horizontal plane transversely to its;

knurling roller l8.

longitudinal axis, the knurl support l4 pivots in.- a counterclockwise direction, as viewed in Fig. 4,, whereby to increase the spacing between the rollers i8 and 33 and thereby accommodate the variation in piston wall thickness at the point of knurling.

The above-described form of my invention possesses an important advantage in that the device is characterized by marked operating sensitivity. The knurling roller is being carried by the short arm of a lever or bell crank comprising the knurl support [4 and the knurling load or pressure being applied manually at the outer end of the long arm 25: of the lever, it will be seen that slight variations in piston wall thickness or other interior surface irregularities will be greatly magnified or emphasized resulting in a correspondingly greater degree of movement at the outer end of the arm 20. This increased degree of movement is immediately apparent to the hand of the operator and he may adjust the degree of downward hand pressure applied on the arm 20 accordingly as the roller l8 rocks inwardly and outwardly of the device. Thus, my device permits the aption of substantially constant knurling pressure, as determined by the hand of the operator on the lever 2B} in response to the rocking movement of the support l4, even when the radial spacing between the rollers l8 and 38 varies as the anvil roller 38 encounters surface irregularities on the interior of the piston skirt.

As hereinbefore mentioned, the diameters and widths of the knurling roller l8 and the anvil roller 38 are preferably substantially the same. Such a relationship insures that the anvil roller will hav an area of engagement with the interior of the piston skirt which lies substantially within the area of engagement of the knurling roller with the exterior of the skirt, thereby avoiding any possibility of undesired peripheral distortion of the piston skirt as a result of the pressure between the knurling and anvil rollers. Of course, the swaging action of the knurling roller results in an increase in the effective diameter of the piston skirt, as hereinbefore described.

Although the invention has been described in detail with reference to one specific structural embodiment, it will be understood that various modifications and equivalent structures may be resorted to without departing from the scope of the invention as defined in the appended claim.

I claim:

A device for knurling the thrust faces of the skirt portion of a piston, comprising an elongated bas having an intermediate portion provided with parallel front and rear sides adapted to be moses-r4:

gripped between the-clamping jaws of a vise; a

bracket-zextendingunwm dly fz om one emiofiaid; base. and: havinga- -bifu rseized- ;rear-31vardly extend mg portion. at its: upper-end: a lever pivotaliy supported within said; reerwardly extending; portion and" having aforwardly extending portion and a depending portion-which i'ssiotted,' a; knur1ingro11errotatably mounted in th slotin. said depend ing -porti0n; 2;; forwardly extend;

ing handlemounted in said forwardly extend;

ing portion, a simila-r1yshaped: btaoket extend'- ing upwardly-- and rearwardly' from the othen end of the-base-, alink *shapedfimilarlx to, said; depending portion and-pjyotally suspendedllfrom said last mentioned; bracket; a shaft rotatablm supported= by saicf limev andi seid depending, Pdri- V tionand cennected-'a;ir-0ne end to. seidikmlfling roller" emit having a handle at its other, end;, a;

third bracketextending; rearwardly andiupward from seidaotnerendoftne basm an elongated 20 3 2 said rollers.

rm; mounte at; ne acumen, ti'fizzd' bnanketr and x nd ng. para lel to. staii ase. 0.1 hat; its. other. ndi st 'adiacent saidknurl ngroller, and an anvil; roller rotat bly mounted. in said, other end of'said armin alignment with.sa,id knurling roller, rsaidiknurling roller being swingable rearwardly towardsa-id. anvil rollerzloy, pressure. downwardly on said forwardly extending. handle to clamp the, skirt otthepistonbetween:

cnnmm JONES.

References Cited. in the; file: of this: patent:

UNITEDi STATES" PATENTS Number Name Date 1 ,414,668 Reed 4 Max 2, 1922; $054,182 Unke Sept. 15;. 1935. $153,363 Fall Apr, 11, 1939;

Wilkinson Febv 23;; 1943 

